The present disclosure relates to wireless communications systems, and more specifically to hybrid closed-loop multiple-input multiple-output (MIMO) and transparent diversity scheme in new radio (NR).
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform-spread-OFDM (DFT-S-OFDM). A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
In some wireless communications systems such as MIMO systems, a base station and UE may use multiple antennas to communicate with each other. The multiple antennas of a base station or UE may, in some cases, be partially coherent. As such, some pairs of antennas (or antenna ports) may be coherent, whereas other pairs of antennas (or antenna ports) may be incoherent. A pair of antennas can be coherent for uplink transmissions if the UE is capable of preserving a phase coherence between the pair. That is, the phases between the pair of antennas are fixed between sounding reference signal (SRS) and physical uplink shared channel (PUSCH). If the base station or the UE is unable to maintain the phase coherence, the pair of antennas can be considered noncoherent (incoherent or not coherent). Such partially coherent condition may be due, for example, to hardware issues of the base station or UE.
In some cases, a pair of antennas that are noncoherent may be restricted from simultaneous transmission with another pair of antennas that are coherent. That is, the base station or UE may be incapable of transmitting on two beams simultaneously—one beam may correspond to a pair of antennas that are coherent and the other beam may correspond to a pair of antennas that are noncoherent—because the transmission from the noncoherent pair of antennas may affect the transmission from the coherent pair of antennas. Limiting transmission for a base station or UE having partially coherent antennas may affect their performance (e.g., time and frequency resources, inefficient power utilization, etc.).